1. Field of the Invention
The invention relates to an apparatus for reproducing image information from a recording medium such as an optical disc or the like.
2. Related Background Art
Hitherto, in case of reproducing information by a pickup from an optical disc on which digital information has been recorded, if a tracking of the pickup is deviated due to a vibration or the like caused from the outside, a continuous reproduction of the recorded information is impossible (in case of audio information, a sound skip occurs).
To prevent such a situation, the information on the disc is preliminarily read out and stored in a memory and, when a sound skip occurs, the information stored in the memory is read out for a period of time during which the pickup is recovered. Such a memory is called a shockproof memory and widely used in a portable music reproducing MD (mini disc) or the like. Since a cheap memory of a large capacity can be obtained owing to the progress of the recent semiconductor technique, most of the sound skip can be avoided.
To assure continuity of the reproduction, it is important to control in a manner such that an underrun state such that all of the information stored in the shockproof memory is read out is not caused for a period of time until the tracking is recovered and the information can be normally reproduced. For this purpose, a technique for reducing the tracking deviation itself or the like by raising a pickup recovering speed (improvement of seeking performance), raising a read-out speed from the disc (in case of an MD, it is set to a speed that is about 4 times as high as a data rate of audio data to be recorded), or improving tracking performance also becomes important.
When the shockproof memory is full, a blank readout of the disc, a stop of the rotation of the disc itself (it is effective for power saving), or the like is usually performed.
There is a random reproducing function as another application of the shockproof memory. It is a function for reproducing music pieces in the order designated by the user, and it is a function which cannot be realized in a medium such as a tape or the like. In a manner similar to the case of the sound skip, even in a range where an underrun is not caused in the shockproof memory, the music pieces can be successively continuously reproduced in free order of music pieces without a waiting time.
However, in the case where the information to be reproduced exists intermittently on the disc due to the repetition of the edition or the like, since the seeking operation is frequently performed, there is a problem such that an underrun of the memory occurs and the reproduction is interrupted or an electric power consumption becomes very large. Particularly, the increase in electric power consumption causes a serious problem because it exerts an influence on a duration time of a battery in case of a portable apparatus.